We have an outdated water rights system in the American West: Water goes to those who claimed it first, whether or not they are putting it to the best use.

This system originated out of practicality. The climate in the West is dry for much of the year, and with Western rivers few and far between, it’s often necessary to invest in storage and conveyance to get water to where it is needed. But the rights to use water were allocated many decades ago, when the region had far fewer people, and before it was widely recognized that the system often short-changed the environment. …